1. Field of the Invention
This invention relates in general to oilfield tools for use in subsea wells, and in particular to a device for assisting in inserting an upper tubular member into a lower tubular member within a well.
2. Description of the Prior Art
There are occasions in oil well operations when an upper tubular member needs to be lowered into the well and stabbed into engagement with a lower tubular member. For example, in one type of subsea well tieback application, a casing will be located below the water surface and within a larger diameter casing. This smaller diameter casing has an open upper end located at the wellhead at the sea floor. The operator lowers an upper string from the surface of the sea down into engagement with the upper end of the casing. This tieback operation requires some type of seals between the upper string and the lower casing.
Metal-to-metal seals are desirable in subsea wellhead applications because of the long life as opposed to elastomeric seals. Metal seals require a very tight fit. Normally, this would require that the upper tubular member have seals which interferingly engage the seals of the lower tubular member in an interference fit. Pushing the two members together can cause damage to the seals because of the interference fit.
Also, even if a good metal-to-metal seal is obtained during the first tieback operation, testing procedures may require that the upper string be disconnected from the lower string, then reconnected again. The metal sealing surfaces might be damaged by the sliding interference fit, detracting from their ability to seal on reconnection.